1. Field of the Invention
This invention relates to rear bicycle suspensions. More particularly, it relates to rear shock absorbing suspensions.
2. Description of the Related Art
Rear shock absorbing suspensions for bicycles, such as a mountain bike, are well known in the art. Most of the prior art designs are configured with a goal of optimizing pedal force neutralization or providing great suspension movement. However, to provide a good all-around freerider bike, a more sturdy and durable the bike is needed. A problem exists in that a great suspension movement usually gives way to poor pedaling performance and vice versa.
To provide a durable suspension it is also desirable to maximize the service life of the shock absorbing member. Most of the prior art designs disclose a shock absorbing member mounted to a lever arm or crank in such a way that the angle between the axis of the shock absorbing member and the axis drawn through the shock absorbing member and the pivotal attachment point of the lever arm is in a range of 50 to 70 degrees, depending on the desired rear axle travel. The effectiveness of this relative mounting angle, in the uncompressed state of the shock absorbing member, is that upon activation of the rear suspension system the lever arm pivots about its pivotal attachment point and compresses the shock absorbing member. Upon full compression of the shock absorbing member the mounting angle approaches or equals 90 degrees.
This produces a wheel rate that can be progressive, linear or a falling rate. In prior art, this change in angle ranges from 20 to 40 degrees. The lever arm then loads the shock absorbing member with a force vector that is tangent to the radius that is defined by the length from the lever arm attachment point and the shock pivotal attachment point, and tangential force vector is perpendicular to the axis drawn between the attachment points. This vector force then has vertical and horizontal forces with respect to the shock absorbing axis. The change in mounting angle produces this side loading of the shock absorbing member with the horizontal force, causing undue friction along the seals, guide bushings and control shaft. The added friction resists allowing the swing arm to rotate upwardly and reduces the smoothness and control of the rear wheel in response to an irregularity in the roadway. The side loading of the shaft also allows for unequal sealing around the shaft allowing dirt and other contaminates inside the shock body. All of these factors contribute to decrease service of life of the shock-absorbing member.
Thus, it is desirable to provide a durable suspension bike that pedals like a hardtail, but soaks up the bumps efficiently. It is also desirable to provide a suspension system which minimizes side loading of the shock absorbing member and can be used in a variety of frame designs leaving designers a wide selection of placement points. It is also desirable to provide a suspension system that is useful with either a four bar linkage or in a single pivot configuration. It is also desirable to provide a rear suspension system that facilitates a rear wheel path which moves up and slightly back during compression to absorb the direction of the forces from the terrain while also maintaining the chain parallel to the suspension path. The present invention satisfies these needs.
Accordingly, it is an object of the present invention to provide a shock absorbing rear suspension system which minimizes side loading of the shock absorbing member and is useful with a variety of frame designs.
It is another object of the present invention to provide a shock absorbing rear suspension which causes the bike to pedal more like a hardtail, but which easily soaks up the bumps.
It is another object of the present invention to provide a shock absorbing rear suspension system that is useful in conjunction with either a 4 bar linkage or in a single pivot configuration.
It is another object of the present invention to provide a main four bar linkage system for optimal cycling performance through control of wheel path and neutralization of pedal forces.
It is another object of the present invention to provide a progressive link mechanism for variable travel independent tuning of spring rate.
It is yet another object of the present invention to provide a rear suspension system that facilitates a rear wheel path which moves up and slightly back during compression to absorb the direction of the forces from the terrain, but which also keeps the chain parallel to the suspension path.